<!DOCTYPE html>
<html>
<head>
  <script src="https://cdn.rawgit.com/konvajs/konva/1.4.0/konva.min.js"></script>
  <meta charset="utf-8">
  <title>Konva Modify Curves with Anchor Points Demo</title>
  <style>
    body {
      margin: 0;
      padding: 0;
      overflow: hidden;
      background-color: #F0F0F0;
    }
  </style>
</head>
<body>
  <div id="container"></div>
  <script>
    var width = window.innerWidth;
    var height = window.innerHeight;

    // globals
    var curveLayer, lineLayer, anchorLayer, quad, bezier;

    function updateDottedLines() {
        var q = quad;
        var b = bezier;

        var quadLine = lineLayer.get('#quadLine')[0];
        var bezierLine = lineLayer.get('#bezierLine')[0];

        quadLine.setPoints([q.start.attrs.x, q.start.attrs.y, q.control.attrs.x, q.control.attrs.y, q.end.attrs.x, q.end.attrs.y]);

        bezierLine.setPoints([b.start.attrs.x, b.start.attrs.y, b.control1.attrs.x, b.control1.attrs.y, b.control2.attrs.x, b.control2.attrs.y, b.end.attrs.x, b.end.attrs.y]);
        lineLayer.draw();
    }
    function buildAnchor(x, y) {
        var anchor = new Konva.Circle({
            x: x,
            y: y,
            radius: 20,
            stroke: '#666',
            fill: '#ddd',
            strokeWidth: 2,
            draggable: true
        });

        // add hover styling
        anchor.on('mouseover', function() {
            document.body.style.cursor = 'pointer';
            this.setStrokeWidth(4);
            anchorLayer.draw();
        });
        anchor.on('mouseout', function() {
            document.body.style.cursor = 'default';
            this.setStrokeWidth(2);
            anchorLayer.draw();

        });

        anchor.on('dragend', function() {
            drawCurves();
            updateDottedLines();
        });

        anchorLayer.add(anchor);
        return anchor;
    }
    function drawCurves() {
        var context = curveLayer.getContext();

        context.clear();

        // draw quad
        context.beginPath();
        context.moveTo(quad.start.attrs.x, quad.start.attrs.y);
        context.quadraticCurveTo(quad.control.attrs.x, quad.control.attrs.y, quad.end.attrs.x, quad.end.attrs.y);
        context.setAttr('strokeStyle', 'red');
        context.setAttr('lineWidth', 4);
        context.stroke();

        // draw bezier
        context.beginPath();
        context.moveTo(bezier.start.attrs.x, bezier.start.attrs.y);
        context.bezierCurveTo(bezier.control1.attrs.x, bezier.control1.attrs.y, bezier.control2.attrs.x, bezier.control2.attrs.y, bezier.end.attrs.x, bezier.end.attrs.y);
        context.setAttr('strokeStyle', 'blue');
        context.setAttr('lineWidth', 4);
        context.stroke();
    }

    var stage = new Konva.Stage({
        container: 'container',
        width: width,
        height: height
    });

    anchorLayer = new Konva.Layer();
    lineLayer = new Konva.Layer();

    // curveLayer just contains a canvas which is drawn
    // onto with the existing canvas API
    curveLayer = new Konva.Layer();

    var quadLine = new Konva.Line({
        dash: [10, 10, 0, 10],
        strokeWidth: 3,
        stroke: 'black',
        lineCap: 'round',
        id: 'quadLine',
        opacity: 0.3,
        points: [0, 0]
    });

    var bezierLine = new Konva.Line({
        dash: [10, 10, 0, 10],
        strokeWidth: 3,
        stroke: 'black',
        lineCap: 'round',
        id: 'bezierLine',
        opacity: 0.3,
        points: [0, 0]
    });

    // add dotted line connectors
    lineLayer.add(quadLine);
    lineLayer.add(bezierLine);

    quad = {
        start: buildAnchor(60, 30),
        control: buildAnchor(240, 110),
        end: buildAnchor(80, 160)
    };

    bezier = {
        start: buildAnchor(280, 20),
        control1: buildAnchor(530, 40),
        control2: buildAnchor(480, 150),
        end: buildAnchor(300, 150)
    };

    // keep curves insync with the lines
    anchorLayer.on('beforeDraw', function() {
        drawCurves();
        updateDottedLines();
    });



    stage.add(curveLayer);
    stage.add(lineLayer);
    stage.add(anchorLayer);

    drawCurves();
    updateDottedLines();
  </script>

</body>
</html>